Local area network for distributing data communication, sensing and control signals

ABSTRACT

A network for carrying out control, sensing and data communications, comprising a plurality of nodes. Each node may be connected to a payload, which comprises sensors, actuators and DTE&#39;s. The network is formed using a plurality of independent communication links, each based on electrically-conducting communication media comprising at least two conductors and interconnecting two nodes, in a point-to-point configuration. During network operation, nodes can be dynamically configured as either data-generating nodes, wherein data is generated and transmitted into the network, or as receiver/repeater/router nodes, wherein received data is repeated from a receiver port to all output ports. During normal network operation, the network shifts from state to state. Each state is characterized by assigning a single node as the data-generating node, and configuring all other nodes in the network as repeaters and receivers. The network can be configured in linear or circular topology, or any mixture of both. The nodes and the payloads can each be powered by local power supply or via the network wiring. In the latter case, dedicated wires can be used, or the same conductors may be employed for both power distribution and communication. Network control can be performed external to the network, or by using the network itself as transport for control messages. Shifting from state to state can be done by selecting sequential nodes to be the data-generating node, or by selecting arbitrary nodes to be the data-generating node.

This is a continuation of parent application Ser. No. 09/349, 020 filedJul. 7, 1999, now U.S. Pat. No. 6,956,826.

FIELD OF THE INVENTION

The present invention relates to the field of wired communication andcontrol networks, and, more particularly, to local area networks andnetworks used for sensing, communication, and control.

BACKGROUND OF THE INVENTION

Local area networks (LANs) for distributing data communication, sensing,and control signals are often based on a “bus” topology, as shown inFIG. 1. Such a network 10 relies on shared electrically-conductingcommunication media 1, usually constituted by a twisted-pair ofelectrical conductors or a coaxial cable. Network data terminalequipment (DTE) units 5, 6, and 7 are connected via respective networkadapters 2, 3, and 4 to communication media 1. Network adapters 2, 3,and 4 function as data communication equipment (DCE) units, and aretapped into communication media 1, forming parallel electricconnections, and thereby interface between DTE units 5, 6, and 7 andcommunication media 1. Such network adapters are also commonly referredto as “NIC”, an example of which is the Network Interface Card IEEE 802(Ethernet). Such a topology is commonly used for connecting personalcomputers (PCs) in a network. Network adapters can be stand-alone units,integrated into the DTE unit or housed therewith in a common enclosure.

Control networks, interconnecting sensors, actuators, and DTE's alsocommonly use the same topology, such as the network described in U.S.Pat. No. 4,918.690 (Markkula, Jr. et al.) and shown in FIG. 2. In anetwork 20, network adapters 22, 23, and 24 function as DCE's, but arecommonly referred to as “nodes”. The payloads 25, 26, and 27 arecomposed of sensors, actuators, and DTE's.

Hereinafter, the term “node” is used for both control anddata-communication applications.

A topology (such as bus topology) whose physical layer communicationmedia employs multi-point connections, is not optimal for communication,and exhibits the following drawbacks:

-   -   1. The maximum length of the communication media is limited.    -   2. The maximum number of units connected to the bus is limited.    -   3. Complex transceivers are required in order to interface the        communication media.    -   4. The data rate is limited.    -   5. Terminators are required at the communication media ends,        thus complicating the installation.    -   6. At any given time, only single connected unit may transmit;        all others are receiving.    -   7. In case of short circuit in the bus, the whole network fails.        Localizing the fault is very difficult.

Despite these drawbacks, however, bus topology offers two uniqueadvantages:

-   -   1. If the application requires “broadcast” data distribution,        where the data generated by a given node must be distributed to        all (or a majority of) the nodes in the network, network        operation is very efficient. This is because only a single        network operation is required (i.e., to establish which node is        the transmitter). The broadcast data is received by all other        nodes in the network in parallel without additional network        overhead.    -   2. The broadcast message is received simultaneously by all        receiving nodes in the network. This is important in real-time        control applications, for example, where orderly operation of        the units must be maintained.

The communication-related drawbacks described above are solved bynetworks constructed of multiple communication links, wherein eachinstance of the link communication media connects only two units in thenetwork. Here, the physical layer in each segment is independent ofother links, and employs a point-to-point connection. Data and/ormessages are handled and routed using data-link layer control. Oneexample of such system for LAN purposes is the Token-Ring, described inthe IEEE 802 standard. An example of a corresponding control network isdescribed in U.S. Pat. No. 5,095,417 to Hagiwara et al. Both networksuse circular topology (“ring topology”) as illustrated in FIG. 3. Anetwork 30 interconnects nodes (or NIC's) 32, 33, and 34 by threeseparate cables 31A, 31B, and 31C, each connecting a pair of nodes andforming three distinct physical layer communication links. Payloads (orDTE's) 35, 36, and 37 are respectively connected to the appropriatenodes.

Both the Hagiwara network and the Token-Ring network use unidirectionalcommunication in each communication link and require a circulartopology. The PSIC network described in U.S. Pat. No. 5,841,360 to thepresent inventor teaches a similar network where the use of a circulartopology is optional, and bi-directional communication (eitherhalf-duplex or full-duplex mode) is employed in the communication links.

The above-mentioned prior art patents and networks are representativeonly. Certain applications are covered by more than one issued patent.Additional discussion concerning the above-mentioned topologies can befound in U.S. Pat. No. 5,841,360 entitled. “Distributed serial controlsystem” which issued Nov. 24, 1998 and co-pending U.S. patentapplication Ser. No. 09/123,486 filed Jul. 28, 1998, both in the name ofthe present inventor, and incorporated by reference for all purposes asif fully set forth herein.

Networks such as those illustrated in FIG. 3 typically use a “store andforward” mechanism, wherein the data received at a specific node isdecoded at least to the data-link layer, and then re-encoded andtransmitted to another point in the network as determined by the networkcontrol. This use of point-to-point communication links eliminates thecommunication drawbacks enumerated above in broadcast-based networks,but it lacks the two unique advantages of the broadcast technology, asalso previously enumerated. Because the data is not inherentlydistributed throughout a network based solely on point-to-pointcommunication links, such a network incurs a heavy overhead whenbroadcast is needed and exhibits delays in the propagation of messages.The overhead and delays result from the need to decode and re-encodemessages at each node.

There is thus a widely-recognized need for, and it would be highlyadvantageous to have, a means of implementing a network which allows forboth improved communication characteristics, while also supportingbroadcast discipline and fast message distribution along the network.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a local area networkin which at least some of the drawbacks described above are reduced oreliminated.

To this end, the present invention provides a local area network basedon nodes connected to payloads. The nodes are interconnected to form anetwork of half-duplex or full-duplex communication links based onelectrically conducting communication media such as twisted conductorpairs or coaxial cables. Each communication link interconnects two nodesin the network. Each node is capable of being dynamically configured asa transmitter or as a receiver. In addition, however, each receivingnode can also be dynamically configured to be a repeater, which simplyretransmits the received data. In this way, data from one link can berepeated to all other links via an automatic multicast process. Innormal operation, a specific node is selected as the data generatingunit to transmit data to the network. All other nodes serve as repeatersand receivers, and hence the data is multicast instantaneously from theselected data generating node throughout the network. After completingthis transmitting session, another node may be selected as the datagenerating node, with all other nodes serving as repeaters and receiversin a like fashion.

A network according to the present invention can also be configured in acircular topology, enabling operation to continue even when there is amalfunction or loss of a communication link.

Therefore, according to the present invention there is provided a localarea network for distributing data communication, sensing, and controlsignals, the local area network including at least three nodes having anoperational mode and interconnected by at least two distinctcommunication links according to a topology, wherein: (a) each of thecommunication links has at least two electrical conductors; (b) each ofthe communication links connects two of the nodes in a point-to-pointconfiguration; (c) each of the communication links is operative tocommunicating in a half-duplex mode; (d) at least one of the nodes isconnected to a payload; (e) at least two of the nodes have theoperational mode selectable as a data-generating operational mode; (f)at least one of the nodes has the operational mode selectable as arepeating operational mode; and wherein the local area network has astate selectable from a group of at least two distinct states, whereineach state is characterized by having a single selected one of the nodesin the data-generating operational mode, with the remainder of the nodesin operational modes selected from a group containing the receivingoperational mode and the repeating operational mode.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, some preferred embodiments will now he described, byway of non-limiting example only, with reference to the accompanyingdrawings, in which:

FIG. 1 shows a prior-art LAN for data communication, employing bustopology.

FIG. 2 shows a prior-art LAN for control, employing bus topology.

FIG. 3 shows a prior-art network for control or data-communication,employing circular topology.

FIG. 4 describes a general block diagram of a node according to thepresent invention.

FIGS. 5 a, 5 b, 5 c, and 5 d show different possible states of a nodeaccording to the present invention.

FIG. 6 shows a state of a network according to the present invention.

FIG. 7 shows a general block diagram of a node according to theinvention, wherein power is also carried by the network.

FIG. 8 shows a state of a network according to the present invention,wherein power is carried by the network and employing circular topology.

FIGS. 9 a and 9 b show different possible states of a node in circulartopology network according to the present invention.

FIG. 10 shows a block diagram of a node according to a preferredembodiment.

FIG. 11 shows a block diagram of a node according to the presentinvention, supporting three line couplers.

FIG. 12 describes various possible node states, and the respectiverequired switches states for a node as shown in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principles and operation of a network according to the presentinvention may be understood with reference to the drawings and theaccompanying description. The drawings and descriptions herein areconceptual only. In actual practice, a single circuit can implement oneor more functions; alternatively, each function can be implemented by aplurality of components and circuits. In the drawings and descriptions,identical reference numerals indicate those components that are commonto different embodiments or configurations.

FIG. 4 schematically shows a node 40 according to the present invention.Node 40 contains the following functional blocks:

-   -   A power supply 41, fed from a power source 52, which converts        incoming power to the voltage, or voltages, required by the node        and the node's components. In addition, power supply 41 may also        feed a payload 49 connected to node 40. If used, this feeding        function is carried out by a payload interface 48. (For clarity,        FIG. 4 omits the individual connections distributing power from        power supply 41 to the power-consuming blocks of node 40.)    -   A payload interface 48 which adapts node 40 to a specific        payload 49. Various payload types can be employed, such as        sensors, actuators and data units, either analog or digital,        functioning either as output or as input. For example:        -   Analog sensor. The payload consists of analog sensor used to            measure any physical phenomena. In most cases, the payload            interface contains an A/D converter.        -   Digital sensor. The payload is a switch, button, etc.        -   Analog actuator. In most cases, the payload contains a D/A            converter controlling the parameters of the analog actuator.        -   Data related unit. In the case of digital communication, the            payload consists of DTE and the payload interface contains a            DTE interface.        -   Non-digital data. Data such as video, voice, analog            communication or any other of data type. If analog data is            input to the node, the payload interface is likely to use an            A/D converter.        -    The above examples are not intended to limit in any way the            general payload definition. Furthermore, multiple devices of            various types can be used. In some cases, payload 49 may use            power from node 40. For example, the excitation voltage to            analog sensor may be driven from the node power.        -    Some nodes in the network may not be connected to a            payload, or may not have any payload interface at all. Nodes            configured in this manner would be used as repeaters only,            such as a node 90 in FIG. 8. Repeater nodes can be used, for            example, to extend the distance between nodes beyond the            regular limit.    -   Line couplers 42 and 43, which interconnect node 40 with up to        two other nodes, each via communication media 50 and 51,        respectively (also referred to as “lines”). Each communication        media supports communication between two nodes of the network.        For clarity only, the two ports are designated ‘Left’-LT and        ‘Right’-RT. The right connection RT uses line 51 and connects        via RT line coupler 43. Similarly, the left connection LT uses        line 50 and connects via LT line coupler 42. Neither line        coupler 42 nor line coupler 43 affects the communication signal.        Line couplers may include connectors, protection devices,        isolation (e.g. transformer) and other required functions, which        are not normally associated with the communication signal        itself.    -   A transmitter 45, which deals with the data to be transmitted,        except for the physical layer functions (according to the OSI        interconnection model). This block can be implemented in        hardware (CRC generation circuitry, for example) by software, or        by both hardware and software.    -   A receiver 46, which deals with the received data except for the        physical layer functions (according to the OSI interconnection        model). This block can be implemented in hardware (CRC error        detection circuitry, for example), by software, or by both        hardware and software.    -   A control, logic, and processing unit 47, which controls and        monitors node 40 and network operation. This block interconnects        with the controlled blocks in node 40 (for clarity, some lines        are omitted from FIG. 4). In addition, control, logic, and        processing unit 47 can process data in the network, and also        deals with the payload via payload interface 48. Control, logic,        and processing unit 47 is furthermore in charge of shifting a        repeater/router 44 from one state to another, as detailed below.    -   Repeater/router 44 deals with the physical layer characteristics        of the communication signal. The repeater/router can be in        various states, including a receive-only state and a        transmit-only state. The signal is encoded and decoded, and is        routed according to the control signals from control, logic, and        processing unit 47. Detailed explanation of the repeater/router        44 follows.

A node can be stand-alone or integrated into the payload. For example,in the case of personal computer, the node can be housed within thecomputer enclosure as an add-on card.

FIGS. 5 a and 5 b describe the various repeater/router functions bymeans of the possible states of a repeater/router during normaloperation. As shown in FIG. 5 a, repeater/router 44 contains two unitsconnected in series. A line receiver 44 b decodes the communicationsignal in the line into a digital signal which is fed to receiver 46 foranalyzing the data-link and higher OSI layers. The digital signal isthen fed to a line driver 44 a which encodes the communication signalagain. The pair consisting of line receiver 44 b and line driver 44 athus form a communication signal repeater which performs a transparentrouting of the communication signal from ‘left’ to ‘right’. The delaybetween input and output is negligible, in the order of nano-seconds ormicro-seconds.

Similarly, FIG. 5 b allows for a routing from ‘right’ to ‘left’. Thedirection of repeater/router 44 is controlled by control, logic, andprocessing unit 47, via control lines (omitted for clarity from FIG. 5).

Whereas FIGS. 5 a and 5 b describe a node which does not generate anydata (but only receives and transfers the data in the network), FIGS. 5c and 5 d illustrate nodes in the transmitting state. In both cases, thenode transmits data to both the right and left connections via therespective line coupler. In FIG. 5 c, two line drivers 44 a are used,one for each direction. In FIG. 5 d, a single line driver 44 a is used,driving both directions from a single unit. Both embodiments can be usedinterchangeably. In most cases, the line driver and line couplercharacteristics will be the basis for selecting one configuration inpreference over the other. For example, if the line driver is capable ofdriving a single line only, the configuration of FIG. 5 c should beused.

FIG. 6 shows a network 60 according to the present invention.Electrically-conducting communication media of lines 61 a, 61 b, 61 c,and 61 d are used to interconnect the nodes. At least two conductors areused in the communication media. For example, coaxial cables or coppertwisted-pairs may be used. For clarity only, the figures hereinillustrate the use of a single twisted-pair in non-limiting examples.

Nodes 62, 63, 64, 65 and 66 are all the based on node 40 as describedpreviously. Nodes 62, 65, and 66 are in ‘Right to Left’ state asillustrated in FIG. 5 b, whereas node 64 is in ‘Left to Right’ state, asillustrated in FIG. 5 a. Node 63 is the data generating node as in FIGS.5 c and 5 d. The network in FIG. 6 shows one possible state of thenetwork, wherein node 63 is the data-generating node, while all othernodes serve as receivers and repeaters, receiving the data andre-transmitting the data to the next sequential node. In order tosupport dynamic reconfiguration, nodes can simultaneously have more thanone operational mode. In a non-limiting fashion, a node can have:

-   -   a data-generating operational mode, wherein a node functions as        a source of data, and transmits this data to other nodes;    -   a receiving operational mode, wherein the node receives data        from another node; and    -   a repeating operational mode, wherein the node functions as a        repeater of data received from one given node by re-transmitting        this data to another given node.

While the network is functioning, the current operational mode of a nodeis selectable from the available operational modes. Some operationalmodes may be mutually exclusive, while others may be selectedsimultaneously. For example, the data-generating operational mode isexclusive of the repeating operational mode, whereas the receivingoperational mode may be selected at the same time as the repeatingoperational mode.

In most applications, more than one node can serve as a data-generatingnode at different times. In such a case, the network states will bechanged as a function of time according to predetermined logic andcontrol, in order to allow each data generating node an opportunity totransmit. However, no more than a single node can serve asdata-generating node at a time. While a node is serving asdata-generating node, all other nodes states are accordingly set to berepeaters and/or receivers, to allow for data distribution along thenetwork. Nodes located ‘left’ of the data generating node will be in a‘right to left’ state, while nodes located ‘right’ of thedata-generating node will be in a ‘left to right’ state.

It should be clear that, whereas the nodes at the network ends, the‘left-most’ node 62 and the ‘right-most’ node 64 could use the samestructure as shown in FIG. 4 (and can be implemented in the same way asall other nodes in the network), the end nodes utilize only single lineconnection. Thus these end nodes can be implemented using a single linecoupler and single line driver.

It should also be clear that one or more of the nodes in the networkneed not be connected to a payload, as is illustrated for node 65 inFIG. 6. This may be the case where the attenuation in the line is toohigh (e.g. a line is too long), and a node serves mainly as a repeater.In such a case, payload interface. 48 would not be required.

Network Powering

FIG. 6 illustrates a network wherein each node is locally powered by alocal power source 52, which supplies electrical power for operating thecomponents of the network. Alternatively, the network communicationmedia can be used for power distribution. In one embodiment of thepresent invention, the power is distributed via dedicated lines, such asby the use of two additional wires within the same cable. In a preferredembodiment, the same wires can be used for both data communication andpower distribution. The latter configuration is described in co-pendingU.S. patent application Ser. No. 09/141,321, filed by the presentinventor on Aug. 27, 1998, which is applicable to the network discussedherein and incorporated by reference. FIG. 8 illustrates such a network,allowing for single power-supply to be used for powering the wholenetwork.

When the same wires are used for both communication and power, the node40 should be modified to include a power/data combiner/splitter 71 asshown in FIG. 7. A node 70 is shown with two power/datacombiner/splitters 71 coupled to line couplers 42 and 43. A node such asnode 70 can receive power from either the left or the right sides orfrom both sides, and carry the power to the non-powered side. Beingpowered from the network, no power source interface will be usuallysupported for such a configuration. The power source feeding the networkcan connect thereto via dedicated couplers or via one or more of thenodes, modified to support such capability.

Circular Topology.

While the foregoing description applies the present invention to alinear topology, the present invention can also be implemented using acircular topology for ‘ring’ type networks. In one embodiment, both endsof the network are connected to a node which is configured to receivefrom both sides, hence including two receivers. However, FIG. 8 shows apreferred embodiment of a network 80. In network 80, all nodes exceptthe data-generating node are configured to the transparent repeaterstate, either uniformly ‘right-to-left’ or uniformly ‘left-to-right’. Anode 90 in the data-generating state is modified as illustrated in FIGS.9 a and 9 b. Node 90 can transmit to one side and receive from theother. In FIG. 9 a node 90 can transmit to the left side and receivefrom the right side. Similarly, in FIG. 9 b node 90 can transmit to theright side and receive from the left side. Either state can be used incircular topology. In FIG. 8, node 90 is in the state shown in FIG. 9 a.Alternatively, node 90 can be in the state shown in FIG. 9 b. All othernodes of FIG. 8 are configured in the ‘right-to-left’ direction. In bothcases, the data-generating node 90 transmits to one side and receivesfrom the other. The receiving functionality of node 90 can be used formonitoring the network, to insure that the data path is available and iserror-free. However, this receiver functionality is an option only, anddoes not have to be implemented.

For compactness, FIG. 8 demonstrates both the power feeding via thenetwork and the circular topology together, but these features areindependent and may be implemented separately.

Network Control.

As described above, the operation of the network (either bus or circulartopology) switches from state to state. Each state is characterized byhaving a specific node functioning as data-generating node at a time,while all other nodes serve as repeaters and receivers, routing the datacoming from the data-generating node. Hence, there is a need for anetwork controller to determine which node in the network will be thedata-generating node.

Various techniques can be used to implement such a network controller.The network controller can select nodes sequentially, by means of tokenpassing from node to node (similar to that of the Token-Ring network).The network controller can be external to the network, using dedicatedcommunication media. Preferably, the network controller will be embeddedand will manage the network states via signals transported by thenetwork itself. In most cases, each node should be allocated an address,enabling data routing in the network from arbitrary node to arbitrarynode.

Another popular method of network discipline is ‘master/slave’operation. In another embodiment of the present invention, one of thenodes will be designated as the master node. In the initial state, thisnode serves as the data-generating node, and while in this state directsother nodes to transmit. During the following state the selected nodewill serve as the data-generating node. This two-state sequence will berepeated, with a different node selected to be the data-generating nodein each subsequent cycle, according to predetermined logic or underexternal control.

Dual Discipline Network.

The network taught by U.S. Pat. No. 5,841,360 to the present inventor,herein referred to as the “PSIC Network”, employs multiple communicationlinks, independent of each other. Such a network supports severalfeatures which are not available in the previously-described network,such as automatic addressing, fault localization, and circular topologyredundancy in the case of single failure.

In order to exploit the benefits of both these network types it ispossible to construct a network which supports both disciplines and canbe controlled to be either in one discipline or in the other. Forexample, the network may start as PSIC Network. During this start-upperiod, automatic addressing and fault. localization will be performed.Thereafter, the network may configure itself to work according to thisapplication or may use time-sharing and alternately switch between bothconfigurations.

FIG. 10 shows a schematic view of a node 100 which is capable of bothroles. The state of node 100 is determined by switches 101, 104, 102,and 103, designated SW1, SW2, SW3 and SW4 respectively. These switchesare controlled by control, logic, and processing unit 47. Node 100employs transmitters 45 a and 45 b, as well as receivers 46 a and 46 b.Line driver 44 a serves the right port, while line driver 44 a 1 servesthe left connection. Similarly, line receivers 44 b and 44 b 1 areconnected to the right and left interfaces respectively.

FIG. 12 lists the various possible node states for node 100 (FIG. 10).The states in FIG. 12 are given in a Node State column, and the switchsettings are given in SW1, SW2, SW3, and SW4 columns. In a‘Right-to-left’ state, data received in the right port is handled byline receiver 44 b and fed to line receiver 46 b. Simultaneously, thereceived data is fed to line driver 44 a 1, which transmits to the leftside. Thus, the functionality shown in FIG. 5 b is obtained. In asimilar way, the ‘Left-to-right’ state is implemented to achieve afunctionality as shown in FIG. 5 a. In the latter case, line receiver 46a is the active one.

In the ‘transmit both sides’ state, transmitter 45 a transmits to bothports using line drivers 44 a and 44 a 1, implementing the functionalityshown in FIG. 5 c. In the ‘receive both sides’ state, each receiver isconnected to single line coupler, and no line driver is activated. Thisis expected to be the state when the network is idle or as an interimstate while switching between states, in order to avoid data collisionscaused by two or more transmitters active over the same link.

The ‘transmit right receive left’ state reflects the state shown in FIG.9 b. Similarly, the ‘transmit left receive right’ state reflects thefunctionality shown in FIG. 9 a.

In the ‘transmit/receive both sides’ state, the node can receive andtransmit in both interfaces simultaneously, thus implementing the fullPSIC Network functionality.

Nodes with More than Two Line Connections

Whereas the foregoing discussion describes a node having two linecouplers (which may be reduced to single interface in the case of anend-unit in a network employing ‘bus’ topology), it is obvious thatthree or more such interfaces could also be used. In such a case, atleast one additional repeater/router must be added for each additionalinterface. For example, FIG. 11 illustrates a node 110 having threeinterfaces, where an additional interface is designated as ‘up’, anduses a line coupler 112 for interfacing to a line 111. In order tosupport the interconnection between all three ports, threerepeater/router units 44 are used, each constructed as describedpreviously and suitable for connecting two ports. In some applications,where the connectivity requirements can be reduced, any two out of thethree ports may be used.

Similarly, additional interfaces can be used. Furthermore, a network canemploy nodes of different interface capacities, which can be freelyconnected to construct a network of arbitrary topology. In all cases,the basic rule that each communication link connect only two nodes mustbe observed. Furthermore, the network logic embedded in the nodes has toinsure that no more than a single node generates data, while all othersmust be in the transparent repeater/router state, directed from thedata-generating node.

Implementation.

Implementing any of the above schemes is straightforward for anyoneskilled in the art. In one embodiment, RS-485 (EIA-485) is employed forthe physical layer. In such a case, line driver 44 a and line receiver44 b are directly implemented using a common RS-485 line driver or linereceiver, respectively. Similarly, the switches illustrated in FIG. 10can be implemented using manually-activated switches, relays, analogswitches, or digital switches/multiplexers. Except in the case of manualswitches, switching is controlled electronically.

Repeaters and regenerators are known in both prior-art WAN (Wide AreaNetwork) and LAN (Local area network) systems, mainly for the purpose ofallowing operation over lengthy connections. However, there are majordifferences between those networks and the present invention. First,most prior-art repeaters employ single input and single output. Thepresent invention allows for multiple ports. Second, prior-art repeatersare unidirectional, while the present invention is not restricted to aspecific direction of data flow. Additionally, the present inventionrequires a control mechanism (a network controller) for determining thedata flow direction, whereas prior-art systems, being unidirectional, donot require such control. In most prior-art networks, units in thenetwork can be clearly defmed as either payload-associated units ordedicated repeaters. Such a distinction is not valid when implementing anetwork according to the present invention, since eachpayload-associated unit in the network also includes the repeaterfunctionality.

Although a network according to the present invention, when configuredin circular topology, can be superficially similar to a. Token-Ringnetwork, there are major differences between them. In a Token-Ringnetwork, there is a single constant direction of data flow. The presentinvention does not impose single direction of data flow, but the flowmay change as part of the network operation. In addition, in Token-Ringnetworks the data-generating unit is sequentially allocated according tothe network topology. In the present invention, the data-generating nodeneed not be chosen according to any specific rule, although sequentialselection of the data-generating node is possible.

While the invention has been described with respect to a limited numberof embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made.

1. A self-contained device for configuring a network by coupling firstand second wiring segments in a building connected for carrying adigital data signal to an analog sensor or actuator, each wiring segmenthaving at least two conductors, the device comprising: a first connectorfor connecting to the first wiring segment; a first set of a line driverand a line receiver coupled to said first connector for serialbidirectional communication of a digital data signal with a furtherfirst set of a line driver and a line receiver over the first wiringsegment; a second connector for connecting to the second wiring segment;a second set of a line driver and a line receiver coupled to said secondconnector for serial bidirectional communication of a digital datasignal with a further second set of a line driver and a line receiverover the second wiring segment; a controller comprising a processor andfirmware coupled to said first and second sets; and a third connectorcoupled to said controller and connectable to the analog sensor oractuator, for coupling the digital data signal, carried over the firstwiring segment, to the analog sensor or actuator; and a single enclosurehousing said first and second sets, said controller and said thirdconnector, wherein: said device is addressable; said third connector isconstructed and connectable for coupling said controller to the analogsensor or actuator; and the analog sensor or actuator is external tosaid single enclosure.
 2. The device according to claim 1, wherein eachof the wiring segments is a twisted wire pair or a coaxial cable, andsaid first and second sets are operative to conduct communication overthe wiring segments.
 3. The device according to claim 1, wherein theserial digital data is packet-based.
 4. The device according to claim 1,further comprising a power supply coupled to said first and second setsfor powering said sets, said power supply being coupled to said firstconnector for being powered by DC power carried over the first wiringsegment.
 5. The device according to claim 1, wherein said device has amanually assigned address.
 6. The device according to claim 1, whereinsaid device has an automatically assigned address.
 7. The deviceaccording to claim 1, wherein said device has an address assigned by adata unit connected to said device.
 8. The device according to claim 1,further operative to power a second device connected thereto.
 9. Thedevice according to claim 1, further operative for powering the analogsensor or actuator when connected to said device.
 10. The deviceaccording to claim 1, wherein said device is further operative to repeatat least part of the serial digital data received from the first wiringsegment to the second wiring segment.
 11. The device according to claim1 further connectable to an analog sensor for measuring a physicalphenomenon, wherein the device further comprises an analog to digitalconverter for converting analog signals from the analog sensor intoserial digital data.
 12. The device according to claim 1 furtherconnectable to an analog actuator for affecting a physical phenomenon,wherein the device further comprises a digital to analog converterconverting serial digital data into analog signals for the analogactuator.
 13. A device for use with first and second wiring segmentseach having two ends and each comprising only two conductors in apoint-to-point connection for conducting half-duplex digital datacommunication of serial digital data, said device comprising: a firstconnector for connecting to the first wiring segment; a first drivercoupled to said first connector for transmitting data to the firstwiring segment; a first receiver coupled to said first connector forreceiving data from the first wiring segment; a second connector forconnecting to the second wiring segment; a second driver coupled toreceive data from said first receiver and coupled to said secondconnector for transmitting the data received from said first receiver tothe second wiring segment; a second receiver coupled to said secondconnector and said first driver for receiving data from the secondwiring segment and for passing the data to said first driver; acomponent data port coupled to said first driver and to said firstreceiver for coupling data carried over said first wiring segment to acomponent; a control logic coupled to said first and second drivers andsaid first and second receivers for placing said device in a selectedone of first and second states; a power connection for connecting to apower source; a power supply including a voltage converter and coupledto said power connection to be powered from the power source, said powersupply being coupled to power said first and second drivers, said firstand second receivers and said control logic; and a single enclosurehousing said first and second connectors, said first and second drivers,said first and second receivers, said component data port, said controllogic, said power connection, and said power supply, wherein: in thefirst state, data received from the first wiring segment via said firstconnector is repeated without format change to the second wiring segmentvia said second connector, in the second state, data received from thesecond wiring segment via said second connector is repeated withoutformat change to the first wiring segment via said first connector, andeach of said first and second connectors has only two connection pointsfor connection to the two conductors of a respective wiring segment. 14.The device according to claim 13, wherein said device is addressable ina network.
 15. The device according to claim 13 further for use with athird wiring segment having two ends and comprising only two conductorsin a point-to-point connection for conducting half-duplex digital datacommunication of serial digital data, wherein said device furthercomprises a third connector for connecting to the third wiring segment,said device is further operative in the first state to repeat withoutformat change data received from the first wiring segment via said firstconnector to the third wiring segment via said third connector, and saiddevice is further operative in the second state to repeat without formatchange data received from the second wiring segment via said secondconnector to the third wiring segment via said third connector.
 16. Thedevice according to claim 13, wherein the two conductors of at least oneof the wiring segments concurrently carry a power signal oversubstantially without interfering with data communication, and saidpower connection is coupled to the power signal via a respectiveconnector for powering at least part of said device.
 17. The deviceaccording to claim 16, wherein said device is further operative to powerat least part of a connected component from the power signal.
 18. Thedevice according to claim 13, wherein at least one of the first andsecond wiring segments is one of a twisted wire pair and a coaxialcable, and respective ones of said connectors, receivers and drivers areadapted for respectively connecting, receiving and transmitting over theat least one of the wiring segments.
 19. The device according to claim13, wherein said device is further operative for analog sensing andcontrol and further comprises an analog port and a converter forconverting between analog and digital signals coupled between saidanalog port and said component data port, and said analog port iscouplable to an analog sensor or to an analog actuator constituting oneof the components.
 20. The device according to claim 19, wherein saiddevice is further operative to carry video or voice signals.
 21. Thedevice according to claim 13 wherein said single enclosure furtherhouses a respective connected component.
 22. The device according toclaim 13 wherein said component data port is a standard DTE interface.23. The device according to claim 13, wherein said device is furtheroperative to be in a third state in which data received from saidcomponent via the component data port is repeated without format changeto both the first wiring segment via said first connector and the secondwiring segment via said second connector.
 24. The device according toclaim 13 wherein the two conductors of at least one of the wiringsegments concurrently are connected to carry a power signalsubstantially without interfering with the data communication, and saidpower connection is further coupled to at least one of said first andsecond connectors for coupling a power signal from the power source overa connected wiring segment.
 25. A device for coupling a data unit to acable having exactly two ends and including two dedicated wires forcarrying a power signal and a single twisted wire pair in apoint-to-point connection for carrying half-duplex digital datacommunication of a serial digital data, the device comprising in asingle enclosure: a wiring connector for connecting to the cable, saidwiring connector having a cable connection side consisting of only afirst pair of connection points for connection only to the two dedicatedwires for carrying a power signal and a only a second pair of connectionpoints for connection only to the single twisted wire pair; a firstdriver coupled to said wiring connector for transmitting data to thecable; a first receiver coupled to said wiring connector for receivingdata from the cable; a data connector for connecting to a data unit forbi-directional standard-based digital data communication with the dataunit, for coupling the data unit to said serial digital data; a seconddriver coupled to said data connector for transmitting data to the dataunit, said second driver being coupled to pass digital data from saidfirst receiver; and a second receiver coupled to said data connector forreceiving data from the data unit, said second receiver being coupled topass data to said first driver, wherein said drivers and receivers arecoupled to said wiring connector to be powered from the power signal.26. The device according to claim 25, wherein said device is addressablein a network.
 27. The device according to claim 25, further comprising apower supply including a voltage converter and coupled to said wiringconnector to be powered from the power signal, wherein the power supplyis coupled to power said drivers and said receivers.
 28. The deviceaccording to claim 25, further comprising a control logic coupled tosaid drivers and receivers for placing said device in a selected one offirst and second states, wherein: in the first state, data received fromthe cable via said wiring connector is repeated without format change tothe data unit via said data connector, and in the second state, datareceived from the data unit via said data connector is repeated withoutformat change to the cable via said wiring connector.
 29. The deviceaccording to claim 25 wherein said data connector is coupled to passpower from said wiring connector for powering a connected data unit fromthe power signal.
 30. The device according to claim 25, in combinationwith a single enclosure disposed within the data unit, wherein saiddevice is housed in said enclosure.
 31. A device for coupling an analogunit to a cable having exactly two ends and including two dedicatedwires for carrying a power signal, and a single twisted wire pair in apoint-to-point connection for carrying half-duplex digital datacommunication of serial digital data, said device comprising: a wiringconnector for connecting to the cable, said wiring connector having acable connection side consisting of only a first pair of connectionpoints for connection only to the two dedicated wires for carrying apower signal and a only a second pair of connection points forconnection only to the single twisted wire pair; a driver coupled tosaid wiring connector for transmitting data to the cable; a receivercoupled to said wiring connector for receiving data from the cable; ananalog connector for connecting to an analog unit; a converter forconverting between analog and digital signals coupled between saidanalog connector, said receiver and said driver, for coupling the serialdigital data to the analog unit; and a single enclosure housing saidwiring connector, said driver, said receiver, said analog connector andsaid converter, wherein said converter, said driver and said receiverare coupled to said wiring connector to be powered from the powersignal.
 32. The device according to claim 31 wherein the analog unit isa video or voice unit, and the cable is further connected to carrydigitized video or digitized voice signals.
 33. The device according toclaim 31, wherein said device is addressable in a network.
 34. Thedevice according to claim 31 wherein the analog unit is an analog sensorfor measuring a physical phenomenon, and said converter is an analog todigital converter.
 35. The device according to claim 31 wherein theanalog unit is an analog actuator for producing a physical phenomenon,and said converter is a digital to analog converter.
 36. The deviceaccording to claim 31 further comprising a power supply including avoltage converter and coupled to said wiring connector to be poweredfrom the power signal, said power supply being coupled to power saiddriver, said receiver and said converter.
 37. The device according toclaim 31 further comprising a control logic coupled to said driver andsaid receiver for placing said device in a selected one of first andsecond states, wherein: in the first state, data received from the cablevia said wiring connector is converted to analog form and passed to theanalog unit via said analog connector, and in the second state, ananalog signal received from the analog unit via said analog connector isdigitized and passed to the cable via said wiring connector.
 38. Thedevice according to claim 31 wherein said analog connector is coupled topass power from said wiring connector for powering a connected analogunit from the power signal.
 39. The device according to claim 31, incombination with a single enclosure disposed within the analog unit,wherein said device is housed in said enclosure.
 40. A device forcoupling to a power signal and a full-duplex serial digital data signalsimultaneously carried over an Ethernet-based local area network (LAN)cable comprising at least one twisted-wire pair, said device comprising:a LAN wiring connector for connecting to the cable; a power/datasplitter having first, second and third ports, said splitter beingconfigured so that only the power signal is passed from said first portto said second port, and only the digital data signal is passed betweensaid first and third ports, and wherein said first port is coupled tosaid LAN wiring connector; a LAN transceiver coupled to said third portof said power/data splitter for point-to-point communication of the fullduplex serial digital data signal with a transceiver of the same type assaid LAN transceiver over said LAN cable; a power supply for voltageconversion coupled to and powered from said second port of saidpower/data splitter, said power supply having a power source portconnected to said LAN transceiver for powering said LAN transceiver fromsaid power supply; a data port coupled to said LAN transceiver andconnectable to a data unit for coupling the packet-based full-duplexserial digital data signal to the data unit; and a visual indicatorpowered by said power supply for indicating the device status, whereinsaid device is addressable in the LAN.
 41. The device according to claim40, wherein said device has a manually assigned address.
 42. The deviceaccording to claim 40, wherein said device has an automatically assignedaddress.
 43. The device according to claim 40, wherein said device hasan address assigned by the data unit.
 44. The device according to claim40 wherein: the data unit is a wired digital data unit; said data portcomprises a digital data connector connectable to the wired digital dataunit; and said device further comprises a further transceiver coupledbetween said LAN transceiver and said digital data connector forbi-directional digital data communication with the wired digital dataunit.
 45. The device according to claim 44 wherein the communicationwith the wired digital data unit is full duplex standard serialcommunication.
 46. The device according to claim 40 further comprisingfirmware and a processor executing said firmware, and wherein saidprocessor is coupled to said LAN transceiver for controlling said LANtransceiver.
 47. The device according to claim 40, wherein said deviceis further operative to power the data unit and said data port iscoupled to said power supply for powering the connected data unittherefrom.
 48. The device according to claim 40, wherein said device isfurther operative for sensing a physical phenomenon, wherein the dataunit is an analog sensor for sensing a physical phenomenon, and saiddevice further comprises an analog to digital converter coupled betweensaid data port and said LAN transceiver for converting analog signals todigital signals.
 49. The device according to claims 48, wherein thedigital data signal contains digitized audio or video data, and thesensor is an audio or video device.
 50. The device according to claim40, wherein said device is further operative for producing a physicalphenomenon, wherein the data unit is an analog actuator for producingthe physical phenomenon, and wherein said device further comprises adigital to analog converter coupled between said data port and said LANtransceiver for converting digital signals to analog signals.
 51. Thedevice according to claim 50, wherein the digital data signal containsdigitized audio or video data, and the actuator is an audio or videodevice.
 52. The device according to claim 40 further enclosed in asingle enclosure with the data unit coupled to said device.
 53. Acontrol device for coupling a component to first and second wiringsegments of a local area network (LAN), each segment having two ends andcomprising a twisted-wire pair having two conductors arranged in apoint-to-point connection for carrying unidirectional digital datacommunication of serial digital data, said device comprising: a firstLAN connector for connecting to the first LAN wiring segment; a firstsignal transformer coupled to said first LAN connector for passing onlydata signals; a receiver coupled to said first signal transformer forreceiving data signals passed by said first signal transformer anddecoding data in the received signals; a second LAN connector forconnecting to the second wiring segment; a second signal transformercoupled to said second LAN connector for passing only data signals; adriver coupled to said second signal transformer for encoding andtransmitting data to said second signal transformer; a component dataport coupled to said driver and to said receiver for coupling datacarried over at least one of the wiring segments to a component; a powerconnection for connecting to a power source; a power supply including avoltage converter and coupled to said power connection to be poweredfrom the power source, said power supply being coupled to power at leastsaid driver and said receiver; and a single enclosure housing said firstand second LAN connectors, said first and second signal transformers,said receiver, said driver, said component data port, said powerconnection and said power supply, wherein at least part of the datareceived from the first wiring segment via said first connector isrepeated without format change to the second wiring segment via saidsecond connector.
 54. The control device according to claim 53, furthercomprising a CRC error detector coupled to said receiver and a CRCgenerator coupled to said transmitter for responding to errors.
 55. Thecontrol device according to claim 53, wherein said device is addressablein a network.
 56. The control device according to claim 53 further foruse with a third wiring segment in the local area network (LAN), thethird wiring segment having two ends and comprising a twisted-pairhaving two conductors in a point-to-point connection for carryingunidirectional digital data communication of serial digital data, saiddevice further comprising a third connector for connecting to the thirdwiring segment, and wherein said device is further operative to repeatwithout format change data received from the first wiring segment viasaid first connector to said the wiring segment via said thirdconnector.
 57. The control device according to claim 53, wherein the twoconductors of at least one of the wiring segments concurrently carry apower signal substantially without interfering with the datacommunication, and said power connection is coupled to the power signalvia a respective one of said connectors for powering at least part ofsaid control device.
 58. The control device according to claim 57,wherein said device is further operative to power at least part of aconnected component from the power signal.
 59. The control deviceaccording to claim 53, wherein: said device is further operative foranalog sensing and control; said device further comprises an analog portand a converter for converting between analog and digital signalscoupled between said analog port and said component data port; and saidanalog port is couplable to an analog sensor or to an analog actuator.60. The control device according to claim 59, wherein said device isfurther operative to carry video or voice signals.
 61. The controldevice according to claim 53, in combination with a single enclosuredisposed within a component that is to be coupled to one of the wiringsegments, wherein said device is housed in said enclosure.
 62. Thecontrol device according to claim 53 wherein said component data port isa standard DTE interface.
 63. The control device according to claim 53,wherein the two conductors of at least one of the wiring segments areconnected to concurrently carry a power signal substantially withoutinterfering with the data communication, and said device further couplessaid power connection to at least one of said first and secondconnectors for coupling the power signal from the power source over aconnected wiring segment.
 64. The control device according to claim 53further comprising a visual indicator powered by said power supply forindicating the device status.
 65. The control device according to claim53, wherein said device is further operative to communicate with anidentical device connected to the other end of one of the wiringsegments.